The present invention relates to a method of producing sanitary articles such as disposable diapers or the like for absorbing body fluids and an apparatus for carrying out the method, more particularly to method and apparatus for producing sanitary articles with improved efficiency.
Sanitary articles used for absorbing body fluids include articles relating to birth, milk wiping materials, diapers, urine absorbing articles, supporters for various parts of the human body, wound bandages, and bandages for ear, nose or other appendages of the human body. The main requirements for such sanitary articles include (1) the ability to maintain close contact with a complicated anatomical shape without displacement, (2) ease of absorption of excrement, blood, body fluids and secretions, (3) the ability to absorb shock and (4) air permeability.
Typical of a sanitary article which satisfactorily meets these requirements is a paper diaper as illustrated in FIG. 6 which is a cross-sectional view and FIG. 7 which is an exploded perspective view. This sanitary article is usually layered, for example a layered structure having three layers including a body contact layer 70, a receptacle-shaped cover 72 for preventing body fluid from permeating into underclothing or the like and an absorptive pad 74 encased in a hollow space as defined therebetween for absorbing a body fluid.
In order to assure that body fluid will permeate through the contact layer 70, a thermally bonded fibrous body fluid permeable material such as paper, unwoven fabric or the like is used for the contact layer 70. A highly absorptive material such as water absorbing paper, cotton-like pulp or the like is used as the absorptive pad 74. For the cover 72, a thermally fusible and body fluid impermeable material such as foamed polyethylene, foamed polypropylene or the like is employed in order to prevent body fluid from permeating into underclothing or the like.
In general, the cover 72 is shaped as a receptacle so as to accommodate the absorptive pad 74 in a hollow space. The cover 72 has a peripheral flange 76 formed integral therewith, and the contact member 70 and the flange 76 are thermally fused to one another to encase the absorptive pad 74 in the receptacle-shaped interior of the cover 72.
A method of producing sanitary articles having three layers is disclosed in U.S. Pat. No. 4,678,527 issued to John Ulman. According to the Ulman patent, a strip of thermally fusible and body fluid permeable sheet material and a strip of thermally fusible and body fluid impermeable sheet material are moved in parallel with one another at the same speed and a plurality of absorptive pads spaced by a fixed distance are positioned between the strips. Both the sheet strips are wider than the absorptive pads. Thereafter, the strips are thermally fused to one another with the use of a pair of pressing and heating tools in such a manner that the absorptive pads are encased therebetween. Thereafter, the thus assembled material is cut around the periphery of each encased absorptive pad. Thus, the cuts are made in areas where the two sheets are thermally fused together to produce the finished sanitary articles.
The method of the Ulman patent offers the advantage that sanitary products can be produced by successive steps with high productive efficiency. However, due to the fact that two sheet strips are thermally fused in such a manner as to surround a plurality of absorptive pads, it follows that the finished products cannot maintain a constant configuration. In other words, the prior art sanitary article tends to deform during usage and to be displaced from the position where it is applied.
To obviate the foregoing problem, a method producing discrete absorbent cores which assure that sanitary articles maintain a predetermined configuration at all times was proposed by U.S. Pat. No. 4,592,708 issued to Feist et al. According to the Feist et al invention, a drum is formed with a plurality of cavities on its peripheral surface, each of which has a configuration identical to that of the core to be produced, and fibers serving as raw material for the core are injected into each cavity at a high speed. A vacuum is maintained in the interior of the drum in order to prevent the fibers from falling off during rotation of the drum. Thereafter, excess fiber is cut off by means of a scraping roll or cutting cylinder whereby a core having a required shape is obtained. Finally, the core is removed from the drum against the effect of negative pressure by an air jet emanating from a blow-off nozzle.
The method of the Feist et al patent is intended to produce only absorbent cores adapted to maintain a predetermined configuration for sanitary articles. However, uniformity in the step of scraping or cutting the fibers is difficult or impossible to achieve. Further, since the method of the patent is intended to produce only absorbent cores as mentioned above, sanitary articles cannot be produced in closely related successive steps, resulting in lower production efficiency.
As will be readily apparent from the above description, the conventional methods for producing sanitary articles all have drawbacks. Where sanitary articles are produced in successive steps with high production efficiency a stable configuration cannot be assured, whereas where covers of a configuration resisting collapse are produced, they cannot be produced with uniformity and moreover production efficiency is low.